Former Tamil Nadu BJP chief K Annamalai has warned the Centre on MDR charges on UPI and has urged that small retailers be shielded from the proposed levy. Annamalai made the appeal in Udupi, a. Udupi, Oct 24: Former Tamil Nadu BJP president and former IPS officer K Annamalai has mounted a strong challenge to the Union government's reported proposal to impose a merchant discount rate (MDR).